Baffled by Binary event.body in Lambda Function

Support
18

@jen

I’m finally getting around to testing the breaking changes you made in https://answers.netlify.com/t/changed-behavior-in-function-body-encoding/18991/1 (that said, this URL no longer seems to be available for some reason). But, I’m still having trouble getting a binary upload to work with application/octet-stream. I’ve updated my test function to use the following code:

var Buffer = require( "buffer" ).Buffer;

export async function handler( event, context ) {

	var bodyBuffer = ( event.body instanceof Buffer )
		? event.body
		: Buffer.from( event.body, ( event.isBase64Encoded ? "base64" : "utf8" ) )
	;

	// Create a copy of the event for echoing that won't include the massive body.
	var eventCopy = { ...event };
	delete( eventCopy.body );

	return({
		statusCode: 200,
		body: JSON.stringify({
			contentType: event.headers[ "content-type" ],
			contentLength: ( +event.headers[ "content-length" ] || "not-provided" ),
			bodyLength: bodyBuffer.length,
			bodyIsBuffer: ( event.body instanceof Buffer ),
			bodyIsString: ( typeof( event.body ) === "string" ),
			bodyIsBase64: event.isBase64Encoded,
			eventCopy: eventCopy
		})
	});

}

Now, if I try to upload a file to the given function, I get the following response:

{
    "contentType": "application/octet-stream",
    "contentLength": 145652,
    "bodyLength": 275070,
    "bodyIsBuffer": false,
    "bodyIsString": true,
    "bodyIsBase64": false,
    .... truncated ....
}

For some reason, the bodyLength is showing about 2x the size of the content-length header.

Also, notice that it is not being Base64 encoded. However, going back to your “breaking changes” announcement from the other week:

If the content-type is anything else, we will base64 encode the body. This will ensure that binary media types like application/octet-stream and application/pdf arrive at their final destinations intact.

From that, I would assume that the body should be Base64-encoded.

I am not sure what I am doing wrong?